Puddles in the Piazza San Marco

In terms of elevation, the Piazza San Marco is one of Venice's lowest points: The Piazza is almost at the same level as the Venetian Lagoon.

Storm sewers in the Piazza empty into St. Mark's Basin (near the entrance to the Grand Canal), and during high tides, it isn't unusual for water to back up through the drains and into the square.

Such flooding is most dramatic during acqua alta (flood tides that occur mostly from October through April), but it can happen at any time of year--even on warm spring and summer days, when children and tourists are fascinated by puddles on the Piazza:

Wading in the Piazza San Marco

Wading in St. Mark's Square, Venice

Flooding in the Piazza San Marco

New iPhone and Android app predicts Venice flooding

hi!tide Venice smartphone appThe city of Venice and software developer Diego Pizzocaro have announced a free smartphone app titled "hi!tide Venice." The app is available in English for both iOS (iPhone) and Android, and it predicts acqua alta (tidal flooding) with data supplied by Venice's official tidal-monitoring and flood-warning service, the Istituzione Centro Previsioni e Segnalazioni Maree.

The app's main screen shows the current tide plus anticipated low and high tides over the next two days. You can click on a daily forecast for a more detailed view that includes an hour-by-hour graph.

You'll also see icons for "Places" and "Ferries" that show current tide levels at main points of interest (such as the Piazza San Marco) and vaporetto piers.

To download the free app from Apple's App Store or the Android Market, click the links on:

City of Venice: Tide Forecast Apps

Last night's flooding in Venice

Last night, Venice had its first acqua alta (high water) of 2011. The 112-cm water level was relatively minor, compared to some acqua alta tides, but it was enough to inundate the Piazza San Marco and other low-lying areas of the city.

Below is a short video that was taken around 11 p.m., at the high point of the acqua alta in our San Polo neighborhood. (If you've spent time in Venice, you'll probably recognize the Fondamenta del Vin, a pedestrian street near the Rialto Bridge where several restaurants have outdoor tables alongside the Grand Canal.)

Friday update: We noticed that the city's warning sirens didn't sound before the acqua alta, as they're supposed to do when the tide is expected to reach 110 cm. A local newspaper, Il Gazzettino, is now reporting that the sirens weren't working because the Centro Maree (Tide Center) hadn't received maintenance funds.